Boring bit or drill



(No Model.)

F G. JOHNSON.

BORING BIT OR DRILL. No. 369,248. Patented Aug. 30,1887

WlTN ESSEQZ 4 I lwvzrwu PK UNlTIED STATES PATENT Orrrcn.

FRANK O. JOHNSON, OF BOSTON, MASSACHUSETTS.

BORlNG BlT OR DRILL.

SPECIFICATION forming part of Letters Patent No. 369,248, dated August30, 1887.

Application filed August 25, 1686. Serial No. 211,701. (No model.)

drill having a cruciform shank with lateral flanges swagcd thereonwithout removal of any of the metal, as hereinafter described.

These flanges are made somewhat thicker and narrower near the end of theshank than elsewhere, the whole construction serving to stiffen andstrengthen the shank and to give a firmer hold upon it by the bit stockor holder in which it is inserted for use. In some cases I reduce thediameter of the end of the shank, as a step preliminary to swaging itinto the cruciform shape peculiar to my invention. By this practice bitsor drills of large caliber, which otherwise would not enter the stock orholder, are made at the end of the shank of proper size to enter and 'beheld by it.

The drawings illustrate my improvement, showing in Figures 1 and 2 adrill in two different posit-ions, and in Fig. 3 a section of the shankat as a", Fig. 1. Fig. 4is a drill with reduced shank, and Fig. 5 thesame with my improvement.

A represents the body of the bit or drill, having at its working end anydesired form or construction, and at its opposite end the constructionpeculiar to my invention. This peculiarity consists in the cruciformshank 13, having swaged flanges formed at and near the end of the toolby a lateral displacement of part of the metal without removing anyportion thereof, and by leaving between said flanges a tongue or rib, d,of the metal undisturbed along a central plane of the shank. By thisconstruction the fiangesc are formed, mainly, of material forcedlaterally from its original position within the periphery of thecylindrical end of the drill into a new posit-ion partly outside of suchperipheral line and partly within it, and the transverse section of theend of the drill is transformed from a circular to a cruciform outline,as indicated in the drawings. The lateral flanges c retain as theirsurface material the skin or outer coating belonging to the drill endbefore their formation, and the-metal lying within this skin iscompacted by the swaging blow and made of increased strength.

The rib d, which is left standing vertically between the parts depressedor compressed and laterally displaced, is slightly lessened in itsheight or diameter, due to the compression exerted on the adjacentmetal. Thus while the flanges c are by the swaging blow thrown somewhatoutside of their original peripheral circle, the ribs (1 are drawnslightly within it. 1

It will be understood that the dies by which this cruciform character isgiven have each a central recess the converse of and corresponding toone of the ribs cl, while the face of the die is otherwise smooth tocorrespond with the Hat or slightly-curved surface of each flange c. Thefaces of the dies will be not quite parallel when at the innermost limitof their stroke, so as to make said flanges thickest at and near theirouter ends and tapering slightly therefrom. This peculiarity isadvantageous in giving the gripping device of the bitbrace ortool-holder a firmer hold upon it when in use.

The tool, having flanges gradually increasing in thickness toward theirouter ends, cannot be disengaged from the chuck or holder when its jawsare closed upon them, and hence will not pull out when in use.

It is obvious that my improvement is applicable to awls, files, chisels,gonges, and a variety of similar small tools which in use are insertedin a removable handle.

Fig. 4 represents a drill the end of which has been reduced in diameterbefore forming the flanges c and ribs (1 on it, so that whensubsequently formed they will not be toolarge for the capacity of theholder. Fig. shows the tool formed by the two successive operations, thetapering or reduced neck e indicating the decrease in diameter. A singleblow of the swaging-dies is sufficient to form the ribs and flanges ineither case.

Tools with cruciform shanks have heretofore been made by milling out andcutting away the metal lying between the. four arms of the cross,thereby breaking the skin and removing part of the metal withoutrelocating and compacting any portion of it, thus weakening instead ofstrengthening it, and

cruciform shank, the two flanges o of which gradually increase inthickness toward their outer ends, substantially as and for the purposeset forth.

In testimony whereof I have signed my name to this specification,in thepresence of tWo subscribing witnesses, on this 23d day of August, A. D.1886.

FRANK G. JOHNSON.

' Witnesses:

A. H. SPENCER, WV. J. J OI-INSON.

